Electrically-ignited detonating or blasting cap



March 5, 1929 A. e. SCHURICHT ET AL ELECTRICALLY IGNITED DETONATING 0R BLASTING CAP Filed Aug. 30, 1924 Patented Mar. I

UNITED STATES ram" o ;FicE.-

ALFONS G; SCHURICH'I. AND JOSEPH D. MONUTT, OF ALTON, ILLINOIS, ASSIGNORS TO WESTERN CARTRIDGE COMPANY, OF EAS'I.AL'1O1\I', ILLINOIS, A. CORPORATION 7 OF DELAWARE.

ELECTRICAIILY-IGNITED DETONATING OR BLASTING. CAP.

Application filed August 80, 1924. Serial No. 785,208.

nals is placed in the open end of the shell with the filament connecting the terminals over the priming charge. Where a fuse is used to' ignite the primer, this fuse is inserted in the open end of the shell.

The function of the priming charge in an electric detonatorloaded with a composition explosive charge is to detonate the primary charge which in turn detonates the main or explosive charge. Where the primary char e consists of straight'inercuric fulminate, t e priming charge itself need'not consist of a high explosive as only a flash is required to detonate the fulminate priming charge. The principal reason for using mercuricfulminate as a priming .charge is simply to obtain the necessary sensitiveness as the fulminate is extremely sensitive to heat, detonating at 160 C. 30 It was found that if mercuric fulminate is used as a charge without the admixture of 0t er su stances, it is-somewhat too brisant to obtain the full detonating power of the remainder of the explosive charge. This was clearly shown in comparative lead plate tests of electric detonators before and after assembling with the firing device. The charged and pressed caps, but without a priming charge, when exploded by means of a fuse, gave uniformly good lead plate tests, whereas caps assembled with thefiring device and exploded by means of an electric current gave very much inferior tests, a large numer roducin only partial penetration of the the explosion of the fulminate in the riming charge is so rapid and violent that it isrupts' the wall of the cap before the explosivewave stead of being directed downwardly into the.

'main charge. In further' substantiation of detonator, a plug carrying the igniter termilea plate. ur explanation for this is that this theory, itwas observed that if additional support is given to the wall of the cap the lead plate test shows decidedly improved results. It is, however, impracticable to a strengthen the cap shell itself.

. One of the-objects of this invention, therefore, is to provide a detonating or blasting cap with a priming or ignitin charge in which the brisance thereof is re need.

In accordance with this invention, a detonating or blasting cap containing an explosive charge of any suitable composition has a priming charge which itself contains a deterrent. While, as previously mentioned, the principal requirement of the priming charge is a hot flame, the substances which can actually be employed are limited on account of the necessity of their having a very low ignition point; Mercuric fulminate having a low ignition point (160 C.) is ideal as far as this is concerned, but as mentioned above, it is objectionable due to its being somewhat too brisant. It was found that theviolence of the explosion could be tuned down without materially affecting the sensitive ness to heat by mixing with it certain other substances. Antimony sulphide has certain advantages, such as ease of mixin and free charging and as it also has a speci c gravity hand, it does not cut down the brisance sufficiently to entirely eliminate caps givin a poor lead plate test. It is also objectiona le when considered from a safety viewpoint. Antimony sulphide, due to its crystalline structure, is a highly frictional material, it being used for this purpose in small arms, caps ort'primers. This necessarily increases the risk involved in mixing and charging and for that reason'it was thought desirable to find some other material;

Another obj ect-of this invention, therefore, is to provide a blastin cap in which the primer not only has a eterrent component to cut 'down the brisance,-but in, which the deterrent is a lubricant as distinguished from a frictional material. 7

Further objects will appear from the (161 tailed descriptiontaken in connection with the accompanying drawing, in which the fig ureis a longitudinal section of'an electrically ignited-detonating or blasting cap.

. Referring to the accompanying drawing,

" 2, timony sulphide,

1 designates a shell of drawn metal, and, .of course, of comparatively light material. This shell contains an explosive charge 2, which may consist of primary and secondary 5 charges, as usual. The explosive charge is covered by a perforated ferrule 3and capped by a primary or igniting charge 4 embodying this invention. Arran ed over the primary or igniting charge is a lament 5 attached to the terminals 60f lead wires 7, which are ar ranged in a plug 8. The detonating or blasting cap is and may be of any suitable and usual construction well known to those skilled in the art.

l/Ve have discovered that a highly suitable substance for admixture with a brisant sub- "stance, such as mercuric fulminate, is litharge or the yellow mon-oxide, of lead. Litharge is obtained in the formof a very fine powder I 50 and it has lubricating properties. While its specific gravity is considerably greater than.

that of mercuric fulminate, its property of clinging to and coating the crystals of fulminate effectually revents segregation. An

ing. crystalline and having approximately thesame size as the fulminate crystals, does not cling to or coat the fulminate crystals. Litharge, on the other hand coats or covers the fulminate crystais -and it is this coating of the crystals whi apparently slows down the s eed of the explosion. \The sensitiveness o the fulminate to heat is not materially affected by mixing with litharge. 1 v

In our experimental work, we found that mixtures containing from forty to fifty 50; per centlitharge and sixty 60) -to fifty 50 per cent mercuric fulminategave'best results, although these percentages may be.

40 somewhat exceeded. It was also found that these two substances mixed readily and that the resulting mixture charged freely. That the two substances mixed are not subject to segregation was demonstrated by shaking some of the caps loaded with this material in an automatic shaker for ten hours and firing In an upright as well as inverted osition.

. Of a lar e number of caps tested in t is manner all nctioned properly. No difficulty-of any ,kind was encountered in either the mix- The improveing or chargin operations. ment found 1n t e lead plate test was remarkable and adecided improvementwas also obtained in the trauzl block expansion. The

sensitiveness of the caps to heat was notmateri'ally affected. It will, therefore, be seen that the invention accomplishes its objects. A detonating or blastin cap is provided in which ignition, even e ectrlcally, is insured. A riming char e consistin of from forty to fty per.

4 cent ithar e an fifty to sixty per cent mercuric fulm-mate is superior to the regular priming charge consisting of antimony sulprimingl charge. In addition to these advantages, t e low cost of the litharge lowers the material cost of the cap, and as no additional labor or o erations are involved, the final A cost of the 'nished product is somewhat lower than that of the regular antimonypriming char e. i

W 1le we have described one embodiment of our invention, it will be understood that the invention is susceptible of various embodiments and to other priming charges than those containing mercuric fulminate. It is further to be understood that while litharge is the most suitable deterrent so far found, other deterrents having the general characteristics of litharge may be used. Furthermore, while we have found certain. proportions of the priming charge and the deterrent preferable, these proportions may be varied within limits. It is further obvious that various changes may be made in details without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be liniited to the details described. i

Having thus described the invention, what is claimed is:

1. Anelectr'ically ignited blasting cap con taining an explosive charge and a priming or iginiting charge therover consisting of a granular brisant substance whose grains are coated with a deterrent.

2. A detonating or blasting cap containing an-explosive charge and a priming charge consisting of a brisant substance and 11 arge.

3. an explosive charge and a priming charge consisting of a brisant substance coated with litharge.

Adetonating or blasting cap contamlng 4. A detonating or blasting cap containing an explosive charge and a priming :consis'tirig ofmercuric fulminate an arge.

5. A detonating orblasting cap containing an explosive charge and a prlmmg charge consisting of from fifty to sixty per cent of mercuric fulminate and fifty to forty per cent of lithar e.

6. An electrlcally i ited blast ng'cap containingan explosive c arge, a priming or 1gniting char e thereover, and containing a deterrent an a filament arranged over the priming'or igniting ch rge. s

In testimony whereof we afiix our signatures this 8th day of Jul 1924.

ALFONS SCHURICHT. JOSEPH. D. MONUTT. 

